Food storage containers are well known in the art. The noted containers generally include a lid that is selectively detachable from a bowl and are commonly designed to provide a variety of features, including being reusable, disposable, microwavable, and the like.
Numerous types of bowl and lid assemblies and means for effecting sealable engagement of a lid on a bowl have been devised. Illustrative are the containers and engagement means disclosed in U.S. Pat. Nos. 6,170,696 and 6,868,980.
One problem associated with conventional, plastic, microwavable containers stems from the rapid temperature changes they must endure. The container must be permitted to vent during microwaving due to the high pressures that arise as moisture in the container contents vaporizes and gas temperatures increase. Thus, the container must be left open to some degree during microwaving. However, it is also desirable to keep the bowl covered as much as possible to prevent the contents from splattering the inside of the microwave.
A further problem often encountered with plastic containers is the poor ability to accommodate a desired amount of produce respiration while maintaining the sealed integrity of the container. As is well known in the art, providing adequate venting (or breathing rate(s)) to accommodate produce respiration can, and in most instances will, enhance produce freshness.
Various methods and container designs have been employed to provide adequate venting of a container during and after microwaving, and to accommodate produce respiration. For example, the prior art is replete with containers that incorporate valves or openable doors in the container base or lid, which allow venting or increased gas exchange. These executions typically result in added cost and complexity in the manufacture of the container. Additionally, venting structure in the form of complex valves with moving parts is difficult to design into a thermoformed plastic part.
A common practice for venting a conventional container is to remove the lid and place it loosely over the container base to accommodate produce respiration and, during microwaving, to allow air and steam to escape. Another common practice for venting a container is to lift a small portion of the lid from engagement with the base (i.e., “crack open” the lid), such as at a corner region of a square or rectangular container. Both of the noted container venting practices will generally accommodate produce respiration. However, in both instances, the container is still subject to leaking, i.e., no longer leak-proof.
The noted container venting practices will usually permit sufficient air and steam to vent during microwaving because the increased pressure within the container will tend to force the container open, increasing any space between the lid and the bowl. There is still a problem, however, with the splattering of food that can occur through any unsealed region between the lid and base. Furthermore, once microwaving is complete, any steam present within the container will cool and the pressure in the container will drop significantly as the pressure differential no longer tends to open the container. The pressure drop creates a vacuum that can suck the lid into a sealed engagement with the base so that sufficient air may not vent back into the container to compensate for the pressure drop. This problem can be aggravated by the accumulation of steam or vapor, which can additionally form a vapor seal between the lid and bowl. The resulting vacuum can permanently damage the container.
It would thus be advantageous to provide a venting container lid having effective, easy to use venting means (i) that is adapted to effectuate sealable engagement of the lid and a container base in a first position and provide an effective air passage when the venting means is in a second position and (ii) can be readily manufactured via a conventional thermoforming process.